The present invention relates generally to home networking, and more specifically to an interface between a digital signal processor (DSP) and an analog front-end (AFE) in high speed communication modems used in home networking.
Nowadays, millions of households are using home networking to share high-speed Internet access, data and multimedia files among various electrical devices in a house, e.g., desktop computers, laptop computers, printers, hard disk drives, digital video recorders (DVRs) and routers. An electrical device, which is a node in the network, may communicate with other devices via a high-speed communication modem. The high-speed communication modem may have a DSP and an analog front-end, which includes a digital-to-analog converter (DAC) on the transmitting side and an analog-to-digital converter (ADC) on the receiving side. A radio frequency (RF) transceiver may be used for wireless communications between a DSP and an analog front-end.
Several home networking standards, such as Multimedia over Coax Alliance (MoCA) and the G.hn Home Networking Standard in the ITU, specify high speed data rates (160 Mb/sec and higher). Accordingly, sampled data, e.g., 10 bits at 200 Mhz sample rate, must be transferred from a DSP to an analog front-end through a high speed parallel interface with a large number of pins or through a very high speed serial interface. The home-networking systems use time division multiplex access (TDMA) to send data across the network. Each node has in its memory a table containing the transmission parameters for connection with other nodes in the network. Some of these parameters, such as the transmitting (Tx) gain and receiving (Rx) gain of an RF/analog front-end are controlled by the DSP and must be transmitted to an RF/analog front-end in a very short interval of time. Known home networking systems use another high speed interface, separated from the interface for transmitting sampled data, to transfer control information such as the transmission parameters between a DSP and an RF/analog front-end. The two interface solution is inefficient and costly.
The JESD204A standard, ‘Serial Interface for Data Converters,’ allows the transmission of sampled data and control information through one serial interface in frames. A frame may comprise various fields, each consisting of, for example, one or more octets of information. The length of each frame and the number of I/Q channel samples to be sent in each packet generally is fixed for a certain application. The JESD204A standard specifies two methods for handling the control information. The first one is to append one control bit to each I/Q channel sample. It means that the ratio between the sampled data rate and the control information rate is fixed, determined by the number of samples in a packet. This in turn may limit the speed at which the control information is updated. The second method is to follow a packet of several samples by a control word, the length of which is equal to the number of control bits per sample times the number of samples. However, the JESD204A standard does not provide details of the control word. In addition, since the control word comes at the end of the frame, there is an additional delay in the processing of the control information.
Therefore, it would be desirable to improve the interface between the DSP and the RF/analog front-end in a high speed communication modem to transfer sampled data and control information efficiently and flexibly.